This is why Google Inc. today has launched Google Play. It is repositioning all of the digital content it sells into one store in what appears to be an attempt to better compete with Apple Inc.’s iTunes and Amazon.com Inc.’s digital offerings.

Starting today, Android Market, Google Music and the Google eBookstore will become part of Google Play. Google will be upgrading the Android Market app to the Google Play Store app over the coming days on smartphones and tablets running Google’s Android mobile operating system. A consumer’s videos, books and music apps will also be upgraded to Google Play Movies, Google Play Books and Google Play Music apps.

Music, movies, books and apps consumers have purchased prior to today all will be available through Google Play, and synchronized between the desktop, smartphones, tablets and other devices. The content is stored in Google’s web servers, accessible via any of the devices.

“Google Play is entirely cloud-based so all your music, movies, books and apps are stored online, always available to you, and you never have to worry about losing them or moving them again,” writes Jamie Rosenberg, Google’s director of digital content, in an official blog post.

With Google Play, consumers can store up to 20,000 songs for free and buy new songs from a selection of millions, Google says. Consumers can access a selection of 450,000 Android apps and games, browse and buy e-books, and rent films from a selection of thousands of titles, including new releases and HD films, Google says.

“Our long-term goal is to roll out as many different types of content as possible to people around the world, and we’ll keep adding new content to keep it fresh,” Rosenberg writes.